Chapter 13 Evidence of Evolution Fossil: ©Lou Mazzatenta/National Geographic Stock Protoarchaeopteryx: ©O. Louis Mazzatenta/National Geographic Stock Copyright © McGraw-Hill Education.  All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education.

Clues to Evolution Lie in the Earth, Body Structures, and Molecules Life on Earth arose 3.8 billion years ago. Changes in body structures and molecules have slowly accumulated through that time, producing the variety of organisms we see today. Section 13.1 Figure 13.2

Clues to Evolution Lie in the Earth, Body Structures, and Molecules Scientists use the geologic timescale to divide the history of the Earth into eons and eras. These periods are defined by major geological or biological events, like mass extinctions. Section 13.1 Figure 13.2

Clues to Evolution Lie in the Earth, Body Structures, and Molecules Researchers analyze fossils, anatomy, and molecular sequences to learn how species are related to one another. Paleontology is the study of fossil remains or other clues to past life. Fossils provided the original evidence for evolution. Ge Sun, et al. "In Search of the First Flower: A Jurassic Angiosperm, Archaefructus, from Northeast China," Science, Vol. 282, no. 5394, November 27, 1998, pp. 1601-1772. ©1998 AAAS. All rights reserved. Used with permission Section 13.1

Clues to Evolution Lie in the Earth, Body Structures, and Molecules Fossils are the remains of ancient organisms. Left fossil: Ge Sun, et al. "In Search of the First Flower: A Jurassic Angiosperm, Archaefructus, from Northeast China," Science, Vol. 282, no. 5394, November 27, 1998, pp. 1601-1772. ©1998 AAAS. All rights reserved. Used with permission; Wood: ©PhotoLink/Getty Images RF; Embryo: ©University of the Witwatersrand/epa/Corbis; Coprolite: ©Sinclair Stammers/Science Source; Trilobite: ©Siede Preis/Getty Images RF; Fish fossil: ©Phil Degginger/Carnegie Museum/Alamy RF; Leaf fossil: ©Biophoto Associates/Science Source; Triceratops: ©Francois Gohier/Science Source Section 13.1 Figure 13.1

13.1 Mastering Concepts What is the geologic timescale? Fossil: ©Lou Mazzatenta/National Geographic Stock Protoarchaeopteryx: ©O. Louis Mazzatenta/National Geographic Stock

Fossils Record Evolution Fossils form in many ways. Section 13.2 Compression fossil of leaf: ©William E. Ferguson Human skull and bone fossil: ©John Reader/Science Source Figure 13.4

Fossils Record Evolution Fossils form in many ways. Section 13.2 Impression of dinosaur skin: ©Dr. John D. Cunningham/Visuals Unlimited Horn coral: ©Robert Gossington/Photoshot Figure 13.4

Fossils Record Evolution Fossils form in many ways. Section 13.2 Figure 13.4 Mosquito trapped in amber: ©Natural Visions/Alamy

Fossils Record Evolution Even though fossil evidence is diverse, it is often challenging—or impossible—to find fossils of transitional forms between groups. The fossil record is incomplete, partly because some organisms (such as those with soft bodies) fail to fossilize. Also, erosion and movement of Earth’s plates might destroy fossils. Section 13.2 Figure 13.3 Ammonite: ©Jean-Claude Carton/Photoshot

Fossils Record Evolution Dating fossils yields clues about the timeline of life’s history. The simpler, and less precise, method of dating fossils is relative dating, which assumes that lower rock layers have older fossils than newer layers. Section 13.2 Figure 12.3 Canyon: ©Terry Moore/Stocktrek Images/Getty Images RF

Fossils Record Evolution Absolute dating uses chemistry to determine how long ago a fossil formed. Radiometric dating is a type of absolute dating that uses radioactive isotopes. Section 13.2 Figure 13.6 Woolly mammoth skeleton: ©Ethan Miller/Getty Images

Clicker Question #1 Which rock layer (A, B, or C) should have fossils with the most carbon-14? A B C Flower: © Doug Sherman/Geofile/RF Canyon: ©Terry Moore/Stocktrek Images/Getty Images RF

Clicker Question #1 Which rock layer (A, B, or C) should have fossils with the most carbon-14? A B C Flower: © Doug Sherman/Geofile/RF Canyon: ©Terry Moore/Stocktrek Images/Getty Images RF

Clicker Question #2 Researchers used a radioactive isotope with a 25,000-year half-life to date a fossil to 100,000 years ago. The fossil contains ____ as much of the isotope as does a living organism. 1/2 1/4 1/8 1/16 1/32 Flower: © Doug Sherman/Geofile/RF

Clicker Question #2 Researchers used a radioactive isotope with a 25,000-year half-life to date a fossil to 100,000 years ago. The fossil contains ____ as much of the isotope as does a living organism. 1/2 1/4 1/8 1/16 1/32 Flower: © Doug Sherman/Geofile/RF

13.2 Mastering Concepts Distinguish between relative and absolute dating of fossils. Fossil: ©Lou Mazzatenta/National Geographic Stock Protoarchaeopteryx: ©O. Louis Mazzatenta/National Geographic Stock

Biogeography Considers Species’ Geographical Locations According to the theory of plate tectonics, Earth’s surface consists of several rigid layers, called tectonic plates, that move in response to forces acting deep within the planet. Section 13.3 Figure 13.7

Biogeography Considers Species’ Geographical Locations Fossils help geographers piece together Earth’s continents into Pangaea. Section 13.3 Figure 13.8

Biogeography Considers Species’ Geographical Locations Biogeography sheds light on evolutionary events. Animals on either side of Wallace’s line have been separated for millions of years, evolving independently. The result is a unique variety of organisms on each side of the line. Section 13.3 Figure 13.9

13.3 Mastering Concepts How have the positions of Earth’s continents changed over the past 200 million years? Fossil: ©Lou Mazzatenta/National Geographic Stock Protoarchaeopteryx: ©O. Louis Mazzatenta/National Geographic Stock

Anatomical Relationships Reveal Common Descent Two structures are homologous if the similarities between them reflect common ancestry. Section 13.4 Figure 13.10

Anatomical Relationships Reveal Common Descent All of these animals, for example, have similar bones in their forelimbs. These similarities suggests that their common ancestor had this bone configuration. Section 13.4 Figure 13.10

Anatomical Relationships Reveal Common Descent Homologous structures need not have the same function or look exactly alike. Different selective pressures in each animal’s evolutionary line have led to small changes from their ancestor’s bone structure. Section 13.4 Figure 13.10

Anatomical Relationships Reveal Common Descent A vestigial structure has lost its function but is homologous to a functional structure in another species. Vestigial hind limbs in some snake species and pelvises in whales are evidence of these organisms’ ancestors. Section 13.4 Mexican-boa-constrictor: ©Pascal Goetgheluck/Science Source Python skeleton: ©Science VU/Visuals Unlimited Figure 13.11

Anatomical Relationships Reveal Common Descent Anatomical structures are analogous if they are superficially similar but did not derive from a common ancestor. None of these cave animals has pigment or eyes. These similarities arose by convergent evolution, which produces similar structures in organisms that don’t share the same lineage. Lack of pigment arose independently in each of these cave animals. Section 13.4 Salamander: ©Francesco Tomasinelli/The Lighthouse/Visuals Unlimited Crayfish: ©Dante Fenolio/Science Source Figure 13.13

Clicker Question #3 The streamlined shapes of dolphins and sharks evolved independently. The body plan of these two animals are homologous. vestigial. analogous. a product of convergent evolution. Both C and D are correct. Flower: © Doug Sherman/Geofile/RF

Clicker Question #3 The streamlined shapes of dolphins and sharks evolved independently. The body plan of these two animals are homologous. vestigial. analogous. a product of convergent evolution. Both C and D are correct. Flower: © Doug Sherman/Geofile/RF

13.4 Mastering Concepts What can homologies reveal about evolution? Fossil: ©Lou Mazzatenta/National Geographic Stock Protoarchaeopteryx: ©O. Louis Mazzatenta/National Geographic Stock

Embryonic Development Patterns Provide Evolutionary Clues Anatomical similarities are often most obvious in embryos. Notice how much more similar human and chimpanzee skull structure is in fetuses compared to in adults. Section 13.5 Figure 13.14

Embryonic Development Patterns Provide Evolutionary Clues Adult fish, mice, and alligators have very different bodies. Their evolutionary relationships are more obvious in embryos. How do similar embryos develop into such different organisms? Homeotic genes provide a clue. Section 13.5 Fish: ©Dr. Richard Kessel/Visuals Unlimited; Mouse: ©Steve Gschmeissner/Science Source; Alligator: USGS/Southeast Ecological Science Center Figure 13.15

Embryonic Development Patterns Provide Evolutionary Clues Homeotic genes control an organism’s development. Small differences in gene expression might make the difference between a limbed and limbless organism. Homeotic genes therefore help explain how a few key mutations might produce new species. Section 13.5 Figure 13.16

Embryonic Development Patterns Provide Evolutionary Clues Mutations in segments of DNA that do not encode proteins also produce new phenotypes. Section 13.5 Figure 13.17

13.5 Mastering Concepts How does the study of embryonic development reveal clues to a shared evolutionary history? Fossil: ©Lou Mazzatenta/National Geographic Stock Protoarchaeopteryx: ©O. Louis Mazzatenta/National Geographic Stock

Molecules Reveal Relatedness Comparing DNA and protein sequences determines evolutionary relationships in unprecedented detail. It is highly unlikely that two unrelated species would evolve precisely the same DNA and protein sequences by chance. It is more likely that the similarities were inherited from a common ancestor and that differences arose by mutation after the species diverged from the ancestral type. Section 13.6

Molecules Reveal Relatedness Molecular clocks assign dates to evolutionary events. If a gene is estimated to mutate once every 25 million years, then two differences from an ancestor might arise in 50 million years. Section 13.6 Figure 13.20

Molecules Reveal Relatedness If a gene is estimated to mutate once every 25 million years, then two differences from an ancestor might arise in 50 million years. Therefore, two species that derived from the same common ancestor 50 MYA might have four differences in the nucleotide sequence of the gene. Section 13.6 Figure 13.20

Clicker Question #4 Mutations in a gene occur at a rate of one nucleotide every 10 million years. The gene sequence differs by 6 nucleotides between two related organisms. How long ago did these organisms split from a common ancestor? about 2 million years ago about 30 million years ago about 60 million years ago about 120 million years ago None of the choices is correct. Flower: © Doug Sherman/Geofile/RF

Clicker Question #4 Mutations in a gene occur at a rate of one nucleotide every 10 million years. The gene sequence differs by 6 nucleotides between two related organisms. How long ago did these organisms split from a common ancestor? about 2 million years ago about 30 million years ago about 60 million years ago about 120 million years ago None of the choices is correct. Flower: © Doug Sherman/Geofile/RF

13.6 Mastering Concepts How does analysis of DNA and proteins support other evidence for evolution? Fossil: ©Lou Mazzatenta/National Geographic Stock Protoarchaeopteryx: ©O. Louis Mazzatenta/National Geographic Stock